Abstract: This paper focuses on studying the effects of hydrogen blend fraction in methane on combustion and NOx emission in tube furnace. Based on a tube furnace, circular burners were tested on furnace #1 and wall-mounted burners were tested on furnace #3. Using Fluent and coupling the FGM combustion model with the detailed reaction mechanism of GRI-Mech 3.0 and the measured temperature of flue gas in hot state, the effects of hydrogen blend fraction in methane on combustion and NOx emission in the tube furnace were numerically calculated. The range of hydrogen blend fraction in methane was controlled between 0% and 60% (hydrogen by volume). The results showed that: 1) as the hydrogen blend fraction increased, NOx emissions increased from 75 mg/Nm³ to 100 mg/Nm³ for furnace #1 and decreased from 63 mg/Nm³ to 50 mg/Nm³ for furnace #3; 2) as the hydrogen blend fraction increased, the hot spot above 1 500 ℃ mainly distributed inside the nozzle of the burner on furnace #1 and kept increasing in area, while it distributed outside the nozzle of the burner on furnace #3 and kept decreasing in area; 3) in terms of energy saving and emission reduction, compared to the hydrogen blend fraction of 20%, the heat transfer efficiency of furnace #1 was improved by 4.53% and that of furnace #3 was improved by 0.52% with a hydrogen blend fraction of 60%, and the carbon dioxide emission reduction in flue gas was 26%; 4) The above results show that hydrogen blend improves NOx emission, but the internal circulation of flue gas in the furnace reduces NOx emission. The final NOx emission result of the burner is affected by the comprehensive effect of hydrogen blend and internal circulation of flue gas.

Key words: tube furnace, hydrogen blend fraction in methane, hot spots, combustion experiment measurement, experimental validation, numerical simulation